Centrifugal clutches are well known; they are used, typically, to connect a drive motor or engine to a load, while permitting the motor or engine to come up to speed from stopped condition without any substantial loading being initially placed thereon, and connecting the design load only when a predetermined speed, at which full torque is developed, has been obtained.
Centrifugal clutches use centrifugal weight which are connected to a coupling element which, in turn, is coupled or connected to a shaft driven by the motor. The centrifugal weights are, customarily, moved due to the rotary movement of the coupling element against the inner surface of a second coupling element which, usually, is drum-shaped or cup-shaped, or bell-shaped, and connected to the output shaft which, in turn, is then connected to the using equipment or machine, for example a rotary cutter, a saw, or other device. When the drive shaft rotates, the engagement force of the centrifugally acting weights becomes effective with the square of the speed. Consequently, by friction, the output shaft and the load connected thereto is gently started, since the increase in speed, due to the initially low frictional engagement of the centrifugally acting element is also still low. When synchronism has been achieved between the driving shaft and the output shaft, the pressure, and hence frictional force of the centrifugal weights is high.
If the output shaft is suddenly blocked, for example if a saw blade coupled thereto meets an obstruction, the clutch is subjected to excessive wear and tear since the driving shaft, in spite of the blocking of the output shaft, continues to rotate, and the frictional engagement force of the centrifugally acting elements continues.
When high power is to be transmitted, blockage of the output shaft can lead to red-hot overheating of the friction surfaces which are customarily present between the centrifugal weights and the cooperating clutch drum within a few seconds, and hence lead to destruction of the clutch mechanism. Repairs require that the entire machine be stopped, parts disassembled and exchanged, all of which is time-consuming and expensive. Additionally, the shock of the sudden blockage is fed back to the driving motor.